STEREO Weekly Meeting Minutes for 2017-10-24 (Week 43) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * Attempts to recover Behind have transitioned from a weekly schedule to a daily schedule. Two days each week use the older 1 kHz frequency acquisition sequence, in case the nominal frequency has shifted, with one day devoted to battery recovery, and one day devoted to carrier recovery. This typically is scheduled for Monday and Tuesday. The remainder of the week uses the faster 4 kHz frequency acquisition sequence. Two of those days use a search pattern consisting of two diamonds, based on the estimated uncertainty in the ephemeris. The double diamond pattern is executed twice, once to send commands, and then again 40 minutes later to listen for the carrier. This search pattern will be run twice a week, once for battery recovery, and once for carrier recovery. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 42 (Oct 16-22) * On day 293 (Oct 20), during the DSS-14 support for Ahead, turbo decoder lock was lost intermittently beginning at 1755z through 1804z, possibly due to weather. This anomaly resulted in the loss of 306 frames of real-time telemetry and SSR data. * On day 293 (Oct 20) , during the ESA Malargue (DSS-84) support for Ahead, the transmitter tripped off at 2052z, immediately after the initial sweep. The second uplink acquisition completed successfully at 2058z. As no monitor data is received from ESA supports, an indeterminate number of telemetry frames dropped at 2126z due to late transition from non-coherent to coherent downlink, most likey of the order of a few seconds of data. * On days 293 and 294 (Oct 20-21), the MOC was on portable generator power as commercial and backup generator power was disabled as high voltage required maintenance was performed on the power substation that feeds the building. Three DSN and one ESA supports for Ahead were conducted satisfactory during this period. Note that as two high voltage breakers need to be refurbished, additional TBD substation maintenance will be scheduled. * On day 294 (Oct 21), during the DSS-14 support for Ahead, command bind dropped at 1850z when attempting to uplink Instrument Stored Command Buffer dump command. MOC command software indicates command was sent, but not acknowledged or radiated. All SSR data were received. * On day 292 (Oct 19), fine pointing on Ahead was lost intermittently beginning at 2104z through 293-0122z, briefly at 293-1818z, 294-1038z and again on 294-1521z for a total of 217 seconds over a ~2 day period due to wheel-speed avoidance failures and attitude transients from momentum redistribution. Fine pointing was well within the 3-sigma prime mission requirement. The worst pointing performance was actually during the last several hours of day 292 when wheels 3 & 4 were at their lowest speeds during the period (<100 rpm) where one would expect to see the worst friction/drag effects. Peak pitch & yaw errors during the period were 22.3 & 15.9 arcsec, respectively. In total there were four periods where wheel avoidance failed. Despite the increased noise transients during the period, overall pointing performance remained quite good. These transients can occur with no gyro operations and are not indicative of any problem with the spacecraft G&C. There have been about four such events on Ahead since 2013. * The average daily science data return for Ahead was 4.5 Gbits during this week. The data return is a bit lower because there were fewer 70 meter passes during the week. This situation is expected to continue for the next two months. * Daily attempts to recover Behind continued. * On day 289 (Oct 16), during a 3.25 hour 4 kHz battery recovery search pattern support for Behind with DSS-14, no commands were transmitted during the support as the transmitter was declared red. See DR #G118560 for more information. * On day 290 (Oct 17), during a 2.5 hour 4 kHz carrier recovery support for Behind with DSS-14, 260 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * On day 291 (Oct 18) during a 3.1 hour 4 kHz carrier recovery search pattern support for Behind with DSS-14, 320 commands were transmitted during the support for carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. All 7 points on the pattern were covered twice. Three commands must be received sequentially to power on the transmitter. * On day 292 (Oct 19), during a 2.5 hour 1 kHz battery recovery support for Behind with DSS-14, 189 commands were transmitted battery state of charge recovery. Due to the duration of the support, only 21 of the 36 frequency segments were commanded. * On day 293 (Oct 20), during a 3.5 hour 1 kHz carrier recovery support for Behind with DSS-14, 361 commands were sent for transmitter carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. Due to the duration of the support and the increased commands for each step, only 19 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * On days 293 and 294 (Oct 20-21), the MOC was on portable generator power as commercial and backup generator power was disabled as high voltage required maintenance was performed on the power substation that feeds the building. One DSN support for Behind recovery was conducted satisfactory during this period. Note that as two high voltage breakers need to be refurbished, additional TBD substation maintenance will be scheduled. * On day 294 (Oct 21), during a 3.2 hour 4 kHz carrier recovery support for Behind with DSS-14, 320 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * On day 295 (Oct 22), during a 3.7 hour 4 kHz carrier recovery support for Behind with DSS-14, the SLE command bind was lost at 1311z. The MOT restored the command bind at 1418z and 240 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * The MOC notes that there have several losses of bind over the last 3-4 days, and are investigating to see if there is a common cause. Week 43 (Oct 23-29) * The station 35 transmitter tripped offline near the end of the Ahead support yesterday (Oct 23). * The SECCHI instrument on Ahead had a watchdog reset sometime after 19 UT yesterday (Oct 23). They will attempt to recover the instrument during the pass that was ongoing at the time of the telecon, but may need to command during the following pass as well. * Telemetry bind was lost early this morning (Oct 24) at around 05:15 during a pass for Ahead. * Tomorrow (Oct 25) is the 11th launch anniversary of the STEREO mission. * A restricted IOnet scan will be performed on the MOC on Thursday, Oct 26. This will occur between tracks. * Ahead has 19 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, three at 240 kbps, and thirteen at 160 kbps (two tracks are using ESA stations). * Recovery tracks for Behind are scheduled every day using the 70-m stations, of 2.5-4 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Tuesday for battery recovery and Wednesday for carrier recovery. Double diamond shaped search patterns will be used on Monday (battery) and Thursday (carrier). * The DSN reports that the station 14 transmitter is currently red. This may affect the next pass for Behind. Week 44 (Oct 30-Nov 5) * Daily standard time in the US ends on Sunday, Nov 5. * Ahead has 16 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, three at 240 kbps, and eleven at 160 kbps. * This is the last week of daily attempts to contact Behind. Recovery tracks are scheduled every day using 70 m stations, of 2-3.2 hour durations. DSN time starting this week is very contentious due to the line-up of multiple missions in the same region of the sky, and the fact that only two 70 meter DSN dishes are operating. Double iamond shaped search patterns will be used on Monday (battery) and Friday (carrier). The 1 kHz frequence segmented acquisition sequence will not be used during the week because of the short track durations. Week 45 (Nov 6-12) * Ahead has 18 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, three at 240 kbps, and thirteen at 160 kbps. Four of these tracks use ESA stations. * Tracks to recover Behind switch to a weekly schedule, with tracks scheduled to keep within the 3 day onboard timer. Behind recovery tracks are scheduled for Tuesday, Friday, and Saturday. The Tuesday and Friday passes will use the double diamond search pattern, with the first for battery recovery, and the second for carrier recovery. Week 46 (Nov 13-19) * A 2.2 hour demonstration track with station 25 is scheduled for Monday, Nov 13. There will be no instrument commanding or SSR playback during this track. * The 104th momentum dump on Ahead is scheduled for Wednesday, Nov 15, with ignition at 16:00 UT. This will be the 23rd dump without using the gyros. * Ahead has 16 tracks during the week, and overall coverage is nominal. There is one track at 720 kbps, three at 240 kbps, and twelve at 160 kbps. Two of those tracks use ESA stations. * Double diamond search patterns for Behind recovery are scheduled for Thursday, Nov 16 (battery) and Saturday, Nov 19. Another recovery track is scheduled for Monday, Nov 13. Week 47 (Nov 20-26) * Thursday, Nov 23, is Thanksgiving. Both Thursday and Friday, Nov 23-24, are holidays at APL. * Ahead has 17 tracks during the week, and overall coverage is nominal There are seven tracks at 240 kbps, and ten at 160 kbps. * Double diamond search patterns for Behind recovery are scheduled for Tuesday, Nov 21 (battery) and Wednesday, Nov 22 (carrier). Another recovery track is scheduled for Saturday, Nov 25. Week 48 (Nov 27-Dec 3) * Ahead reaches perihelion on Dec 3. * Ahead has 15 tracks during the week, and overall coverage is short by about 8 hours of 70 meter time between Tuesday and Sunday. There is one track at 720 kbps, four at 240 kbps, and ten at 160 kbps. With the current schedule, the in situ intrument partitions are expected to overwrite for several hours several days in a row. The MOC is looking into possible options to increase the coverage. One of the 70 meter tracks for Behind has been reallocated to Ahead, and two ESA passes have been added to the schedule. * Double diamond search patterns for Behind recovery are scheduled for Tuesday, Nov 28 (battery) and Friday, Dec 1 (carrier). Week 49 (Dec 4-10) * The 41st SECCHI stepped calibration roll is scheduled for Tuesday, Dec 5, starting at 08:55 UT. System momentum will be about 1 N-m-s. This will be the perihelion roll, and will be the 10th roll without gyros. * Ahead has 14 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, four at 240 kbps, and eight at 160 kbps. There is a possibility of data loss if the recorders are still full at the beginning of the week. * Double diamond search patterns for Behind are scheduled for Tuesday, Dec 5 (battery) and Wednesday, Dec 6 (carrier). An additional recovery track is scheduled for Saturday, Dec 9. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 43: M Oct 23 (296) T Oct 24 (297) W Oct 25 (298) 11th anniversary of STEREO launch T Oct 26 (299) F Oct 27 (300) S Oct 28 (301) S Oct 29 (302) Notes: * Behind recovery attempts each day. The Tuesday and Wednesday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Monday (battery) and Thursday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 44: M Oct 30 (303) T Oct 31 (304) W Nov 01 (305) T Nov 02 (306) F Nov 03 (307) S Nov 04 (308) S Nov 05 (309) Daylight savings time ends in US Notes: * Behind recovery attempts each day. Double diamond shaped search patterns on Monday (battery) and Friday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 45: M Nov 06 (310) T Nov 07 (311) Behind: Recovery track, DSN 14 (search pattern, battery) W Nov 08 (312) T Nov 09 (313) F Nov 10 (314) Behind: Recovery track, DSN 14 (search pattern, carrier) S Nov 11 (315) Behind: Recovery track, DSN 14 S Nov 12 (316) Notes: * Behind recovery attempts switch back to weekly, roughly every 2-3 days. ------------------------------------------------------------------------------- Scheduled activities for Week 46: M Nov 13 (317) Ahead: Demonstration track with station 25 Behind: Recovery track, DSN 63 T Nov 14 (318) W Nov 15 (319) Ahead: Momentum dump, 16:00 UT T Nov 16 (320) Behind: Recovery track, DSN 63 (search pattern, battery) F Nov 17 (321) S Nov 18 (322) Behind: Recovery track, DSN 63 (search pattern, carrier) S Nov 19 (323) ------------------------------------------------------------------------------- Scheduled activities for Week 47: M Nov 20 (324) T Nov 21 (325) Behind: Recovery track, DSN 63 (search pattern, battery) W Nov 22 (326) Behind: Recovery track, DSN 14 (search pattern, carrier) T Nov 23 (327) Thanksgiving F Nov 24 (328) S Nov 25 (329) Behind: Recovery track, DSN 14 S Nov 26 (330) ------------------------------------------------------------------------------- Scheduled activities for Week 48: M Nov 27 (331) T Nov 28 (332) Behind: Recovery track, DSN 63 (search pattern, battery) W Nov 29 (333) T Nov 30 (334) F Dec 01 (335) Behind: Recovery track, DSN 63 (search pattern, carrier) S Dec 02 (336) S Dec 03 (337) Ahead: Perihelion ------------------------------------------------------------------------------- Scheduled activities for Week 49: M Dec 04 (338) Ahead: SECCHI stepped calibration roll, 08:55 UT T Dec 05 (339) Behind: Recovery track, DSN 63 (search pattern, battery) W Dec 06 (340) Behind: Recovery track, DSN 63 (search pattern, carrier) T Dec 07 (341) F Dec 08 (342) S Dec 09 (343) Behind: Recovery track, DSN 63 S Dec 10 (344) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2018: * Mar 5 Ahead: Mercury transit 2019: * Mar Ahead: Switch downlink rate to 240 kbps for 34 meter * Apr Behind: Switch downlink rate to 240 kbps for 34 meter 2020: * May Behind: Switch downlink rate to 360 kbps for 34 meter * Jun Ahead: Switch downlink rate to 360 kbps for 34 meter * Jun Behind: Switch downlink rate to 480 kbps for 34 meter * Sep Ahead: Switch downlink rate to 480 kbps for 34 meter 2021: * Jul Behind: Switch downlink rate to 720 kbps for 34 meter * Aug Ahead: Switch downlink rate to 720 kbps for 34 meter 2022: 2023: * May 5 Behind: Mercury transit * Jul 17 Behind: Closest approach to Earth * Aug 13 Ahead: Closest approach to Earth 2024: 2025: * Apr 7 Ahead: Mercury transit 2026: 2027: * Feb 1 Behind: Mercury transit 2028: 2029: * Jun 30 Ahead: Mercury transit